CAPTURA. Repositorio Academico de la Universidad de Chile
(5.176 recursos)
Captura almacena y conserva la producción de conocimiento generado por docentes e investigadores de la Universidad de Chile, y la hace visible desde los portales académicos internacionales.
2.
Synthesis, structure and antifungal properties of Co(II)-sulfathiazolate complexes - Bellú, Sebastián; Trapé, Marcela; Trossero, Claudia; Molina, Gabriel; Drogo, Claudia; Williams, Patricia; Atria, Ana María; Muñoz, Juan Carlos; Zacchino, Susana; Sortino, Maximiliano; Campagnoli, Darío; Rizzotto, Marcela
he reaction between sulfathiazole and cobalt(II) leads to a pink solid, [Co-II(ST)(2)(H2O)(4)] (1), which, after 7-10 days in the mother solution, transforms into red crystals of [Co-II(ST)(2)(H2O)(3)](n) (2) (ST = sulfathiazolate). The Co(II) ion exhibits an octahedral environment in both compounds. Differences between them were noted in the IR spectra in the region corresponding to signals of the amine group. Antifungal properties of (1) were evaluated, showing activity against both Aspergillus fumigatus (the same as the ligand) and Aspergillus flavus (better than the ligand).
3.
Scanning electrochemical microscopy (SECM) study of superoxide generation and its reactivity with 1,4-dihydropyridines - Bollo, S.; Jara Ulloa, Paola Andrea; Finger, S.; Núñez Vergara, Luis J.; Squella, J. A.
A scanning electrochemical microscope (SECM), in the tip generation substrate collection and feedback modes, was used in a method to characterize the electrode mechanism of the O-2/O-2*(-) couple in dimethylsulphoxide (DMSO) containing 0.1 M tetrabutylammonium perchlorate (TBAP) as the supporting electrolyte. Also the quantification of the interaction between O-2*(-) and different 1,4-dihydropyridine compounds is reported.
The SECM results demonstrated that the O-2/O-2*(-) couple follows an E mechanism, in contrast with the EC2 mechanism (DISPs) that was previously reported by cyclic voltammetry. This result implies that in the time scale of SECM measurements there is no time for a homogeneous chemical reaction...
4.
Melt grafting of itaconic acid and its derivatives onto an ethylene-propylene copolymer - Bruna, J.; Yazdani Pedram, M.; Quijada, Raúl; Valentín, J. L.; López Manchado, M. A.
An ethylene-propylene copolymer (EPR) was functionalized in the melt by grafting with itaconic acid and its mono- and di-methyl esters by using dicumyl peroxide as radical initiator. Grafting reactions were carried out in a Brabender-Plasticorder at 180 degrees C under a nitrogen flow at a speed of 75 rpm for 6 min. Fourier transform infrared spectroscopy (FTIR) was used to confirm the existence of grafted monomers. The absorption bands characteristic of each monomer grafted were observed in the FTIR spectrum of the modified EPR and were taken as evidence of grafting.
The percentage of grafting attained was also followed by FTIR...
5.
Asymmetric hydroformylation of vinyl arenes catalyzed by furanoside diphosphinites-Rh(I) complexes - Guimet, Eugeni; Parada, José; Diéguez, Montserrat; Ruiz, Aurora; Claver, Carmen
Diphosphinite ligands 2 and 3, easily prepared from inexpensive D(+)-xylose in few steps, were tested in the Rh-catalyzed asymmetric hydroformylation of several vinyl arenes. High regio-selectivities in branched aldehyde (up to 99%) and moderate enantio-selectivity (up to 63%) were found (20-40 degrees C, 30-60 bar of syn gas). For the first time, the structure in solution of the species formed under hydroformylation conditions with diphosphinite ligands was determined
6.
Fast high performance liquid chromatography and ultraviolet-visible quantification of principal phenolic antioxidants in fresh rosemary - Troncoso, N.; Sierra, H.; Carvajal, L.; Delpiano, P.; Günther, Germán
An improved HPLC method is reported for the determination of rosemary's principal phenolic antioxidants, rosmarinic and carnosic acids, providing a fast and simultaneous determination for both of them by using a solid phase column. The analysis was performed with fresh methanolic extractions of Rosmarinus officinalis. To quantify the amount of antioxidants in a fast and reproducible way by means of UV-vis absorption measurements, a spectrophotometric multi-wavelength calibration curve was constructed based on the antioxidant contents obtained with the recently developed HPLC method. This UV-vis methodology can be extended to the determination of other compounds and herbs if the restrictions mentioned...
7.
Study of the release mechanism of diltiazem hydrochloride from matrices based on chitosan-alginate and chitosan-carrageenan mixtures - Tapia, C.; Corvalán, V.; Costa, Edda; Gai, María Nella; Yazdani Pedram, M.
The aim of this work was to establish the diltiazem hydrochloride release mechanism from the chitosan-alginate matrix tablet (MCB/AS) and chitosan-carrageenan matrix tablet (MCS/CSI). The weight loss for MCS/CSI is mainly due to the weight loss of the matrix while for MCB/AS it is mainly due to the diltiazem hydrochloride released from the tablet. Using the Peppa's model the release order for MCS/CSI was n = 1.07 +/- 0.13 and for MCB/AS was n = 0.76 +/- 0.02. Thus, MCS/CSI has a transport mechanism, and for MCB/AS the drug release mechanism is a combined process of diffusion and relaxation. MCB/AS...
8.
Electrochemical reduction of C-4 nitrosophenyl 1,4-dihydropyridines and their parent C-4 nitrophenyl derivatives in protic media - Núñez Vergara, Luis J.; Santander, Paola; Navarrete Encina, P. A.; Squella, J. A.
A comprehensive study of the electrochemical reduction in protic media of parent C-4 nitrophenyl 1,4-DHPs and their corresponding nitrosophenyl 1,4-DHPs was carried out. The reduction potentials of synthesized aromatic nitro compounds were compared with those of the corresponding nitroso compounds, concluding that the latter were reduced at significant more positive potentials. Arylhydroxylamines formed in the 4-electrons reduction of nitrophenyl 1,4-DHPs at acid pH can be protonated and further reduced. At pH12, in some compounds the 1-electron reduction to give the nitro radical anion could be distinguished from the cyclic voltammograms. Ortho-nitro derivatives were reduced at more negative potentials than other...
9.
Unexpected diastereotopic behaviour in the H-1 NMR spectrum of 1,4-dihydropyridine derivatives triggered by chiral and prochiral centres - Da Silva, Jaqueline; Barría, Claudio; Jullian, Carolina; Navarrete, Patricio; Nuñez, Luis; Squella, J. A.
1,4-dihydropyridine derivatives constitute an important pharmacological group for the treatment of cardiovascular diseases. We have synthesised a series 4-(5'-nitro-2'-furyl)-1,4-dihydropyridine derivatives, which were characterised by H-1-NMR. We have found that carboethoxy groups at the C-3 and C-5 on the 1,4-dihydropyridine ring show a much more complex signal in the H-1 NMR spectra, either when C-4 is a pseudo-prochiral or a chiral centre.
10.
Reaction of singlet molecular oxygen, O-2((1) Delta(g)), with the Cinchona tree alkaloids - Effect of absolute configuration on the total rate constant - Lemp, Else; Günther, Germán; Castro, Rafael; Curitol, Manuel; Zanocco, Antonio
Detection of O-2((1)Delta(g)) emission, lambda(max) = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, k(T), and the reactive reaction rate constant, k(R), for the reaction between singlet oxygen and the Cinchona tree alkaloids, cinchonidine, cinchonine, quinine and quinidine in several solvents. In most solvents, the kT values were close to 10(7) M(-1)s(-1), indicating that these compounds are good singlet oxygen quenchers. The reactive rate constants are smaller than 10(4) M-1 s(-1), implying that quenching is essentially a physical process. The analysis of solvent effect on k(T) by using LSER equations indicates...
11.
IGF-1 protects cardiac myocytes from hyperosmotic stress-induced apoptosis via CREB - Maldonado, Carola; Cea, Paola; Adasme, Tatiana; Collao, Andrés; Díaz Araya, Guillermo; Chiong, Mario; Lavandero, Sergio
Hyperosmotic stress stimulates a rapid and pronounced apoptosis in cardiac myocytes which is attenuated by insulin-like growth factor-1 (IGF-1). Because in these cells IGF-1 induces intracellular Ca2+ increase, we assessed whether the cyclic AMP response element-binding protein (CREB) is activated by IGF-1 through Ca2+ -dependent signalling pathways. In cultured cardiac myocytes, IGF-1 induced phosphorylation (6.5 +/- 1.0-fold at 5 min), nuclear translocation (30 min post-stimulus) and DNA binding activity of CREB. IGF-1-induced CREB phosphorylation was mediated by MEK1/ERK, P13-K, p38-MAPK, as well as Ca2+/calmodulin kinase and calcineurin. Exposure of cardiac myocytes to hyperosmotic stress (sorbitol 600 mOsm) decreased IGF-1 -induced...
12.
Potato tuber isoapyrases: Substrate specificity, affinity labeling, and proteolytic susceptibility - Kettlun, Ana María; Espinosa, V.; García, L.; Valenzuela, María Antonieta
Apyrase/ATP-diphosphohydrolase hydrolyzes di- and triphosphorylated nucleosides in the presence of a bivalent ion with sequential release of orthophosphate. We performed studies of substrate specificity on homogeneous isoapyrases from two potato tuber clonal varieties: Desiree (low ATPase/ADPase ratio) and Pimpernel (high ATPase/ADPase ratio) by measuring the kinetic parameters K-m and k(cat) on deoxyribonucleotides and fluorescent analogues of ATP and ADP. Both isoapyrases showed a broad specificity towards dATP, dGTP, dTTP, dCTP, thio-dATP, fluorescent nucleotides (MANT-; TNP-; ethene-derivatives of ATP and ADP). The hydrolytic activity on the triphosphorylated compounds was always higher for the Pimpernel apyrase. Modifications either on the base or...
13.
Hydroesterification versus hydroformylation-acetalization of 1-hexene catalyzed by soluble carbonylrhodium complexes of pyridine ligands - Pardey, Alvaro J.; Uzcátegui, Gabriela C.; Hung-Low, Fernando; Rivas, Angel B.; Yáñez, Jorge E.; Ortega, Marisol C.; Longo, Clementina; Aguirre, Pedro; Moya, Sergio A.
The rhodium(l) complexes, cis-[Rh(CO)(2)(amine)(2)] (PF6) (amine = pyridine, 2-picoline, 3-picoline, 4-picoline, 3,5-lutidine or 2,6-lutidine) dissolved in methanol under carbon monoxide atmosphere are effective catalysts for the hydroesterification and hydroformylation-acetalization of 1-hexene. In the presence of these soluble complexes, 1-hexene, CO and methanol give methyl-heptanoate and 1, 1-dimethoxy-heptane as major products, and minor amounts of heptanal. The acetal product comes from the nucleophilic addition reaction of the methanol with the formed heptanal. Gaseous by-products (H-2 and CO2) from the catalysis of the water-gas shift reaction (WGSR) are also observed. The reaction products distribution depends on the nature of the coordinated amine...
14.
Development and validation of an UV derivative spectrophotometric determination of Losartan potassium in tablets - Lastra, Olga C.; Lemus, Igor; Sánchez, Hugo J.; Pérez, Renato F.
Development and validation of an analytical UV derivative spectrophotometric method to quantify Losartan potassium used as a single active principle in pharmaceutical forms were done. Pharmacopeias have not yet provided an official method for its quantification. A study was carried out of all the parameters established by USP XXIV to validate an analytical method for a solid pharmaceutical form, i.e. linearity, range, accuracy, precision and specificity. All these parameters were found in accordance with the acceptance criteria of Comite de Guias Oficiales de Validacion de la Direccion General de Control de Insumos para la Salud de Mexico. Based on the...
15.
Use of an "acetaldehyde clamp" in the determination of low-K-M aldehyde dehydrogenase activity in H4-II-E-C3 rat hepatoma cells - Moncada, Claudio; Fuentes, Nelson; Lladser, Alvaro; Encina, Gonzalo; Sapag, Amalia; Karahanian, Eduardo; Israel, Yedy
The high-affinity (K-M < 1 muM) mitochondrial class 2 aldehyde dehydrogenase (ALDH2) metabolizes most of the acetaldehyde generated in the hepatic oxidation of ethanol. H4-II-E-C3 rat hepatoma cells have been found to express ALDH2. We report a method to assess ALDH2 activity in intact hepatoma cells that does not require mitochondrial isolation. To determine only the high-affinity ALDH2 activity it is necessary to keep constant low concentrations of acetaldehyde in the cells to minimize its metabolism by high-KM aldehyde dehydrogenases. To maintain both low and constant concentrations of acetaldehyde we used an "acetaldehyde clamp," which keeps acetaldehyde at a concentration...
16.
Studies on quinones. Part 38: Synthesis and leishmanicidal activity of sesquiterpene 1,4-quinones - Valderrama, Jaime A.; Benites, Julio; Cortés, Manuel; Pessoa Mahana, Hernán; Prina, Eric; Fournet, Alain
The reaction of (+)-euryfuran 1 with several benzo-, naphtho- and benzo[b]thiophene-1,4-quinones in acetic acid yields the corresponding euryfuryl-1.4-quinones 3, 5, 7, 8, 10, 12, and 14. The structure of compounds 7, 8, 12, and 14 was assigned through 2D NMR H-1-C-13 HMBC experiments. The influence of the acidity of the solvent upon the reactivity and regioselectivity of the quinones to the oxidative coupling reaction, is discussed. The in vitro activity of the euryfurylquinones and their corresponding precursors against Leishmania amazonensis is described.
17.
Longitudinal analysis of metalloproteinases, tissue inhibitors of metalloproteinases and clinical parameters in gingival crevicular fluid from periodontitis-affects patients - Pozo, P.; Valenzuela, María Antonieta; Melej, C.; Zaldívar, M.; Puente, Javier; Martínez, B.; Gamonal Aravena, Jorge
Background: The aim of this work was to improve the assessment of the periodontal disease status through measurements of extracellular matrix metalloprote nases (MMPs) and their tissular inhibitors (TIMPs) in the gingival crevicular fluid from patients diagnosed with chronic periodontitis.
Methods: Gingival crevicular fluid samples from patients (n = 13) were taken from 60 site:; initially. and from 51 and 41 sites, respectively. 3 and 6 months after scaling and root planing. Gingival crevicular fluid samples were also taken from healthy subjects (n = 11, 24 sites). The presence of MMP-9 and MMP-8 was assessed by zymography and immunowestern blotting, respectively....
18.
Inhibition of tumor necrosis factor alpha secretion and prevention of liver injury in ethanol-fed rats by antisense oligonucleotides - Ponnappa, Biddanda C.; Israel, Yedy; Aini, María; Zhou, Feng; Russ, Rachel; Cao, Qing-na; Yiyang, Hu; Rubin, Raphael
Elevated serum tumor necrosis factor alpha JNF-alpha) levels predict mortality in patients with alcoholic liver disease. Administration of anti-TNF-alpha antibodies, obliteration of Kupffer cells or gut sterilization protect against ethanol-induced hepatocellular injury in animal models. In this study, we evaluated the in vivo efficacy of an antisense phosphorothioate oligodeoxynucleotide (S-ODN) targeted against TNF-alpha mRNA (TJU-2755). Naive rats that were administered TJU-2755 (10 mg/(kg body weight (BW)/day) for 2 days) in the free form were challenged with LPS to induce TNF-alpha secretion. Antisense TJU-2755 treatment reduced serum TNF-a levels by 62%. A comparison of the efficacies of mismatched and random S-ODNs...
19.
Nifedipine and nitrendipine reactivity toward singlet oxygen - Pizarro Urzúa, Nancy A.; Núñez Vergara, Luis J.
The ability to generate singlet molecular oxygen, O-2((1)Delta(g)), and the scavenging activity of two well-known 1,4-dihydropyridines (1,4-DHPs) such as nifedipine (1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-3,5-pyridine-dicarboxylic acid dimethyl ester) and nitrendipine (1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridine-dicarboxylic acid ethyl methyl ester) is assessed.
Results show that nifedipine does not generate O-2((1)Delta(g)) under our experimental conditions. In contrast, this 1,4-dihydropyridine behaves as a good scavenger of excited oxygen, mainly via physical deactivation with values of the total rate constant ranging from 20.8 x 10(5) M-1 s(-1) in dioxane to 93.0 x 10(5) M-1 s(-1) in propylencarbonate. The less favored reactive pathway generates a photooxidation product, which has been isolated and identified by...
20.
Cyclic voltammetry and scanning electrochemical microscopy studies of the heterogeneous electron transfer reaction of some nitrosoaromatic compounds - Bollo, S.; Finger Caraccioli, Sebastia?n Nicola?s; Sturm, J. C.; Núñez Vergara, Luis J.; Squella, J. A.
The heterogeneous electron transfer reaction for the reduction of some nitroso aromatic derivatives in aqueous-alcoholic medium was studied on both mercury and glassy carbon electrodes (GCE) by using cyclic voltammetry (CV) and scanning electrochemical microscopy techniques (SECM).
The nitrosoaromatic derivatives followed a two-electron two-proton mechanism producing a quasi-reversible overall process. This strongly pH dependent mechanism varied from ECCE mechanism at pH < 8.5 to ECEC mechanism pH > 8.5.
The apparent heterogeneous rate constant for the reduction of the nitroso derivatives was calculated using CV or SECM. The rate constant for the electron transfer process depends on the nature of the electrode...
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